C1 Brake upgrade question.

[Bruce B.]

On my 57 Corvette Gasser project I am making 1 modern improvement and that is using a dual master cylinder with a GM combination proportioning valve.
I have Airheart disc brakes on the front and Olds drum brakes on the back.
I questioned one of the big aftermarket brake system suppliers about using DOT 5 in the system.
He told me DOT 5 is not good for the whole brake system and it would swell the rubber components in the master and wheel cylinders and that DOT 5 fluid is junk.
I respected his opinion until he said the DOT 5 was junk.
I have used DOT 5 in my 57 and my 62 and never had any rubber swell or general brake problems.
Both systems were rebuilt with what I would call regular off the shelf rebuild kits which I would guess use modern polymers which I would think are also used in the upgraded system.

I obviously do not want to risk brake failure, but on the other hand I think DOT 5 fluid is superior to DOT 3 and 4.

Any opinions would be appreciated.

[Steven B.]

Re: C1 Brake upgrade question.

Bruce, I have used Dot 5 in my '77 since the early 80's with no problems. I put the Dot 5 in when I had my calipers ss'd. The '57 and '78 have non-silicone in since new and no problems due to the fluid. I am sure there will be more replies.

Bruce, do you have pictures of the gasser? Did you get the axle out?

Steve

[Duke W.]

Re: C1 Brake upgrade question.

Problems can develop when DOT 5 gets mixed with DOT 3 or 4. This can happen when guys try to "upgrade" to DOT 5 by using the bleed to flush method. There is no way in hell you can purge all the old DOT 3 or 4 this way, and the fluids are neither miscible nor compatible, and then problems start.

That's why my recommendation is that if you want to change to DOT 5, you have to start with everything completely disassembled, cleaned, and dried, which includes the master and wheel cylinders. Then you assemble all the hydraulic components with DOT 5. Brake pipes can be thoroughly flushed with denatured alcohol and dried with compressed air. New brake hoses should see the same treatment since the ends are swaged on using DOT 3 as a lubricant.

Done the above way the system is much better protected from internal corrosion, so periodic fluid changes are virtually eliminated, but I'd still do it at least every 10-15 years.

Duke

[John F.]

Re: C1 Brake upgrade question.

I have done both of my 62s just as Duke outlines.
John F

[Bruce B.]

Re: C1 Brake upgrade question.

Duke,
I'm starting with a completely new brake system, my concern was with what the tech guy at the brake company said.
As I stated I have used DOT 5 in a few of my cars and always with a completely new system and no problems.
Bruce B

[Bruce B.]

Re: C1 Brake upgrade question.

57 REAR END++ 002.jpg57 REAR END++ 008.jpg57 REAR END +++ 001.jpg57 REAR END +++ 003.jpg
Steve,
Attached are a few pics from the 57.
The rears show the difference in size between the Olds and the 57 Corvette. The Olds weights a ton.
The brake drum is from the Olds rear, the shield on the edge is different, got any idea why it's on the drum?
The interior shot shows the 2 different types of seats, rolled and pleated and button & tuft.
Tomorrow I start on the brakes, I need to relocate the proportioning valve and fabricate all the lines.
So far everything is going well.
I had a 327 (337 CI 0.060 over) built but I also got a Ohio George built engine which I am thinking about selling. It's is a 8 to 1 blower motor, 377 CI stroker that has never been started. Built with good sixties & early seventies parts: Crankshaft Co 1/2" crank, ForgedTrue pistons, Sig Erson Cam Mondello heads, Hooker fenderwell (excellent chrome) headers 2" primaries with 3 1/2" collecters, early hydroformed Lakewood bellhousing and lots more.
In addition I got about 300+ nos GM parts in the boxes.

A fun project to say the least.
Bruce B

[Jim L.]

Re: C1 Brake upgrade question.

I questioned one of the big aftermarket brake system suppliers about using DOT 5 in the system.
He told me DOT 5 is not good for the whole brake system and it would swell the rubber components in the master and wheel cylinders and that DOT 5 fluid is junk.
I respected his opinion until he said the DOT 5 was junk.

Toro poo.

The man's opinion is junk.

Both of our road racing Corvettes (one of which appears in my avatar) have used DOT 5 fluid exclusively. Never, never, never one single problem.

In fact, the use of DOT 5 fluid has meant that the ritual of pre-race brake bleeding has been completely unnecessary.

I use DOT 5 fluid in all of my vintage cars, some of which were converted 30+ years ago. At the risk of being repetitious, never, never, never one single problem.

Jim

[Duke W.]

Re: C1 Brake upgrade question.

I have never heard of anyone having any kind of problem with DOT 5 long term, including me, if the conversion was done as I recommended - everything disassembled, clean and dry - not one molecule of DOT 3 or 4 left, and then assembled with DOT 5 and properly bleed to expell any and all entrained air.

Guys try to do a Mickey Mouse conversion and then blame it on the product when the real problem was POOR WORKMANSHIP!

Duke

[Bruce B.]

Re: C1 Brake upgrade question.

Guys,
Thanks for all the information and opinions.
Today I'm going to mount the master cylinder and start on the plumbing.
I will use DOT 5 and followup with the results.
Thanlks again,
Bruce B

[David G.]

Re: C1 Brake upgrade question.

Bruce,
All good advice above.
I have used Dot 5 for the last 25-30 years in my Corvettes and have not experienced
any problems. I don't think that our military would be using it in trucks if it was JUNK.
I haven't been brave enough to use it in my Hill Climb Corvette or the Bonneville Corvette,
but the next time that I rebuild those systems, I may give it a try.

Regards, Dave Gray.

[Jim L.]

Re: C1 Brake upgrade question.

I haven't been brave enough to use it in my Hill Climb Corvette or the Bonneville Corvette,
but the next time that I rebuild those systems, I may give it a try.

.

See my earlier posting about having used DOT 5 in our two road racing Corvettes.

The time-honored tradition calls for bleeding the brakes before a race.

I'm too frappin' lazy to bleed brakes that often.

Since the "wet" boiling point of DOT 5 is very nearly equal to the "dry" boiling point, it seemed to me that I wouldn't need to bleed brakes very often. It turned out that, after the initial bleeding to get rid of system air, I never had to bleed the brakes again until other factors required that I opened up the system. That was, typically, after a couple of thousand racing miles (approximately 20 - 25 race weekends).

I doubt that any form of racing is any harder on brake fluid than road racing. So, if I can get away with racing with DOT 5, anybody ought to be able to. I wouldn't hesitate to use DOT 5 in a hill climber or in a Bonneville racer.

Jim